Glaxo Smith Klyne fined $4.2 BILL for killing kids., page-22

Well known culprit, Helicobacter Pylorii, is the cause of over 80% of gastric ulcer conditions causing discomfort. Triple antibiotics (2 pills only per day total) for a 10 day period knocks it on the head for good. Zantac/other proton pump inhibitors are largely out of fashion now. Note that the nerve that goes to your stomach (Vagus nerve) isn't real specific about where pain comes from and quite often ulcer symptoms will feel like reflux (in reality a distance of 15 cm internally).

Gastric reflux is a leak in the valve at the top of the stomach joining the esophagus, allowing the leak of stomach acid and contents into an area of the GIT that does not tolerate the acid burns (eosophagus) giving you pain. This is the clinical definition: http://www.mayoclinic.org/diseases-conditions/gerd/basics/definition/con-20025201
It has nothing to do with the amount of acid in the stomach, only where it ends up.

Simple ways to avoid gastritis pain such as not going for a sleep or lie down immediately after eating, not eating too much, drinking adequate water with meals (~600ml) can all assist in minimising the discomfort, before trying ANYTHING else.